New miniaturized clean-up procedure for hair samples by means of microextraction by packed sorbent: determination of cocaine and metabolites.

Cocaine is still one of the most commonly used illicit substances worldwide, with an estimated 4 million users in Europe in the last year. Hair samples have been widely used for the determination of episodic or repeated consumption of this substance, but the use of miniaturized techniques for hair sample clean-up has been challenging due to the sample complexity. Despite hair's complex matrix, MEPS provides a method that is fast, reduces the volume of extraction solvents used, and offers low-cost options (since extraction beds may be reused several times). Microextraction by packed sorbent using a mixed-mode sorbent was optimized for hair sample clean-up in order to determine cocaine, benzoylecgonine, ecgonine methyl ester, norcocaine, cocaethylene and anhydroecgonine methyl ester by gas chromatography coupled to tandem mass spectrometry. The method was fully validated according to internationally accepted criteria, presenting good linearity between the limits of quantification (0.01-0.15) and 5 ng/mg. Precision and accuracy resulted in coefficients of variation typically lower than 15%, with mean relative errors within ±15% for all compounds, except for the limit of quantification (±20%). The present work describes the first application of microextraction by packed sorbent for the concentration of cocaine and metabolites extracted from hair samples. Graphical abstract.